By combining an Electrospray ionization source and one or more Time of Flight mass filters, one may begin to exploit an important biomedical Mass Spectrometry technique on an instrument platform which is inherently simple in both design and operation, inexpensive and capable of performing the most rigorous time resolved analyses of chromatography effluents. The overall goals of the subject study are two-fold. First, to identify and characterize the operating behavior of such an ESPI-TOF instrument, seeking to optimize both sensitivity and resolution. Specifically, this will entail studies of ion packet formation strategies, comparisons of performance between linear and reflection TOF machines, tandem TOF analyses using both surface and channel induced dissociation, and duty cycle optimization via ion storage. Secondly, implementing this technique, to begin developing a commercially viable instrument by constructing a prototype complete with both data acquisition and data analysis hardware and software. As a complete, turn-key "add-on" to existing LC or CZE devices, this instrument would offer unprecedented scanning speed and mass range, while also providing very high sensitivity and adequately high resolution to perform both molecular weight and structured analyses of biologically important molecules.